High #3 CHT and cold #4

fresh rebuild IO360A1A dual PMAGs with jumper, timed 2 teeth past TDC with about 10 or so hrs on her.

New everything, having to push 12.5GPH to keep number 3 below 380-385 in cruise. Only way I can keep it cool is to LOP

Have the washer in number 3 baffle, everything sealed with RTV, front baffle block offs in front of 1/2.

Cooling ramps installed on top cowling, but the sides aren’t sealed if that makes sense, it’s just the ramps glassed to the cowling.

#4 is running 310 when #3 is pushing 380, oil cooler mounted on baffle behind #4. EGTS way lower on 4 also


Thinking the lower baffles may be too tight around the cylinder not allowing airflow, but previous to overhaul I didn’t have such a big issue. Any tips?

Pics attached, LOP/ROP

Mag checks good? EGT rise on all cylinders during the mag check?

I would do a quick GAMI check to see if you have a lean cylinder as the first step. If so, then round up the usual suspects and run it to ground.

Carl

I'm having random thoughts, but I'll add to Carl's queries...do an in-flight mag check and see if one of the ignitions provides different values than the other. How certain are you that the timing was set correctly? Are the P-Mags new, or just put back on the rebuilt engine? Is the plane new to you? If you built it once before and are familiar with what's "right", it narrows the list down of things to ask. Especially when it comes to baffles and baffle seals. If this is all mostly new to you, then there are a plethora of questions to ask. BTW, the EGTs look lower than I'd expect when you're ROP.

Look at pic 2 - the lop one. Egts ALL over the map - 1100-1400. Think you have issues with fuel injector balancing. In pic 1, chts 1-3 are pretty normal and well grouped. 4 is way low, but look at the egt -100* cooler. Again fuel distribution.

I would start with injector flow balancing instead of cooling air issue.

D-Dubya said:

I'm having random thoughts, but I'll add to Carl's queries...do an in-flight mag check and see if one of the ignitions provides different values than the other. How certain are you that the timing was set correctly? Are the P-Mags new, or just put back on the rebuilt engine? Is the plane new to you? If you built it once before and are familiar with what's "right", it narrows the list down of things to ask. Especially when it comes to baffles and baffle seals. If this is all mostly new to you, then there are a plethora of questions to ask. BTW, the EGTs look lower than I'd expect when you're ROP.

Click to expand...

New ASP rebuild, everything new other than cases. PMags are new to me and used 113s that have the updated stuff to 114s. Pretty confident they’re timed right as the timing procedure is pretty simple.

Agreed on injector balancing, did a gami test on the flight and I believe the spread was .7 or so from memory.

I need to call airflow performance once I get er fully broken in.


Do most people seal their cooling ramps on the sides or leave them open and just have the baffling material run along it?

So is #3 your first cylinder to go lean? I can't tell from the display. Your GAMI spread of 0.7 GPH could be improved upon. However, your absolute EGT values would point to a spread even larger than what you remember. That's not always telling the entire story, though. FWIW, 380 degree CHT in the summer isn't bad, but the 70 degree spread points to some differences that could be looked at.

As far as the top cowling ramps go, I would think the ends don't need to be sealed as long as the baffle seals are installed properly. How about some pics with the top cowl off?

ERJDriver said:

Do most people seal their cooling ramps on the sides or leave them open and just have the baffling material run along it?

Click to expand...

FWIW, My previous RV-8 has the baffles sealing around the bottom of the cooling ramps, with the cooling ramps closed so there is no flow through them.



My current RV-8 has the baffles running along the sides of the cooling ramps and they are open.

Both airplanes have Lycoming PV 180HP engines and they run very similar CHTs and oil temps, both cool. Note that my previous RV-8 has 10:1 high compression pistons.

BTW, it would help if you noted somewhere what RV you are flying.

Got ya, sorry I’m so used to posting in the 8 forum I forgot, it’s an 8A. My baffling is setup like your pic you circled excepts its a 45* and not the swoop shape yours has.

RV8JD said:

My current RV-8 has the baffles running along side the cooling ramps and they are not sealed.


Both airplanes have Lycoming PV 180HP engines and they run very similar CHTs and oil temps, both cool. Note that my previous RV-8 has 10:1 high compression pistons.

BTW, it would help if you noted somewhere what RV you are flying.

Click to expand...

D-Dubya said:

So is #3 your first cylinder to go lean? I can't tell from the display. Your GAMI spread of 0.7 GPH could be improved upon. However, your absolute EGT values would point to a spread even larger than what you remember. That's not always telling the entire story, though. FWIW, 380 degree CHT in the summer isn't bad, but the 70 degree spread points to some differences that could be looked at.

As far as the top cowling ramps go, I would think the ends don't need to be sealed as long as the baffle seals are installed properly. How about some pics with the top cowl off?

Click to expand...

Planning on getting those once I get back in town and pull the cowls for the 10hr oil change